NMEGylation: A Novel Modification to Enhance the Bioavailability of Therapeutic Peptides

We have evaluated NMEGylation-the covalent attachment of an oligo-N-methoxyethylglycine (NMEG) chain-as a new form of peptide/protein modification to enhance the bioavailability of short peptides. OligoNMEGs are hydrophilic polyethylene glycol-like molecules made by solid-phase synthesis, typically up to 40 monomers in length. They have been studied as nonfouling surface coatings and as monodisperse mobility modifiers for free-solution conjugate capillary electrophoresis. However, polyNMEGs have not been demonstrated before this work as modifiers of therapeutic proteins. In prior published work, we identified a short peptide, C-20, as a potential extracellular inhibitor of the fusion of human respiratory syncytial virus with mammalian cells. The present study was aimed at improving the C-20 peptide's stability and solubility. To this end, we synthesized and studied a series of NMEGylated C-20 peptide peptoid bioconjugates comprising different numbers of NMEGs at either the N- or C-terminus of C-20. NMEGylation was found to greatly improve this peptide's solubility and serum stability; however, longer polyNMEGs (n > 3) deleteriously affected peptide binding to the target protein. By incorporating just one NMEG monomer, along with a glycine monomer as a flexible spacer, at C-20's N-terminus (NMEG-Gly-C-20), we increased both solubility and serum stability greatly, while recovering a binding affinity comparable to that of unmodified C-20 peptide. Our results suggest that NMEGylation with an optimized number of NMEG monomers and a proper linker could be useful, more broadly, as a novel modification to enhance bioavailability and efficacy of therapeutic peptides. (C) 2011 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 96: 688-693, 2011.